Biological control programs provide a great opportunity to
study the ecology of the introduced agent in its new environment. Since the species being introduced is not
present in the new ecosystem, one of the most interesting aspects to study is
its rate of dispersal. Estimates of the dispersal rate of the biocontrol agent
in its new environment are vital to understanding its relative searching
capacity, and to foresee the maximum area that could be covered in a
parasitoids’ release event. The objective of this experiment is to study the
dispersal behaviour of one generation of the recently introduced biocontrol
agent Cotesia urabae, to fight the gumleaf skeletoniser Uraba lugens in New Zealand.
It was found that C. urabae dispersed up to 20 m away
from the release point and was most successful parasitizing hosts located no
more than 5 m from the release point. A high level of parasitism was observed
at the epicentre itself (81.5%) which suggests that most of the females
released stayed in the release tree. According to the dispersal model adjusted
from the data collected, Cotesia would be able to disperse up to 53 m in
one release event.
Additionally, statistically significant differences (P < 0.001) were
found between the different directions tested for dispersal. These results suggest that wind has a direct
effect on the dispersal behaviour of C. urabae in the field, showing a
clear downwind dispersal, in this case to NE and E directions.